1. Field of the Invention
This invention relates generally to tools used to complete subterranean wells. More particularly the present invention describes a means of pressure testing the effectiveness of a zonal isolation system after installation.
2. Description of Related Art
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production of oil and gas can begin.
Sand or silt flowing into the wellbore from unconsolidated formations can lead to an accumulation of fill within the wellbore, reduced production rates and damage to subsurface production equipment. Migrating sand has the possibility of packing off around the subsurface production equipment, or may enter the production tubing and become carried into the production equipment. Due to its highly abrasive nature, sand contained within production streams can result in the erosion of tubing, flowlines, valves and processing equipment. The problems caused by sand production can significantly increase operational and maintenance expenses and can lead to a total loss of the well. One means of controlling sand production is the placement of relatively large sand (i.e., xe2x80x9cgravelxe2x80x9d) around the exterior of a slotted, perforated, or other type liner or screen. The gravel serves as a filter to help assure that formation fines and sand do not migrate with the produced fluids into the wellbore. In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the unconsolidated formation that is to be completed for production. The screen is typically connected to a tool that includes a production packer and a cross-over, and the tool is in turn connected to a work or production tubing string. The gravel is pumped in a slurry down the tubing and through the cross-over, thereby flowing into the annulus between the screen and the wellbore. The liquid forming the slurry leaks off into the formation and/or through the screen, which is sized to prevent the gravel in the slurry from flowing through. The liquid that passes through the screen flows up the tubing and then the cross-over directs it into the annulus area above the packer where it can be circulated out of the well. As a result of this operation, the gravel is deposited in the annulus area around the screen where it forms a gravel pack. The screen prevents the gravel pack from entering into the production tubing. It is important to size the gravel for proper containment of the formation sand, and the screen must be designed in a manner to prevent the flow of the gravel through the screen.
At times it is desirable to complete a zone and then isolate the zone until production is initiated at a later date. One example of when delayed production might be beneficial is when multiple productive zones having significantly different formation pressures are to be completed in a single well. If a first zone having greater formation pressures is completed with a second zone that has lower pressures, hydrocarbons from the first zone will migrate to the second zone and may decrease the ultimate recovery that is obtained from the first zone. To maximize the ultimate recovery from the well, it may be beneficial to initially produce only the first zone with the higher pressure. Once the formation pressure of the first zone has decreased to where it is close to the formation pressure of the second zone, the second zone can be produced along with the first zone, and the commingled zones can be depleted together without any loss of reserves from interzonal migration. Economically it would be beneficial to complete both zones while the drilling/completion equipment is on the well, but isolate the second zone until production is desired at a later date.
Zonal isolation systems are used to isolate and selectively produce oil or gas from separate zones in a single well. U.S. Pat. Nos. 5,579,844; 5,609,204 and 5,988,285 describe systems for the zonal isolation of wells. The high variability in downhole conditions and well tool configurations create a need for testing the integrity of zonal isolation systems after their installation. If a zone is not adequately isolated, substantial quantities of hydrocarbon reserves can be lost, resulting in significant economic losses. One method of testing the integrity of zonal isolation system is by running in the well with one or more packer assemblies on a workstring. The packers are set to isolate individual segments of the isolation system, which can then be tested for any leakage. This method requires additional trips in and out of the wellbore that results in increased expense. Any reduction in the number of trips required to complete a well will result in significant cost savings.
There is a need for improved tools and methods to test the integrity of zonal isolation systems after their installation.
One embodiment of the present invention is a zone isolation apparatus for use in completing a wellbore comprising a sand screen assembly and a tubular string disposed within the wellbore. Also included is an isolation assembly that is movable within the sand screen assembly and capable of being selectively positioned in an open configuration and a closed configuration, and a test assembly attached to the tubular string and capable of being selectively positioned in an open configuration and a closed configuration. When the isolation assembly is in its closed configuration fluid communication through the sand screen assembly is restricted, and when the test assembly is in its open configuration, hydraulic communication of the isolation assembly with the surface is achieved. The test assembly can be retained in the closed configuration by a releasable retaining element and can further comprise a sliding sleeve having at least one aperture and a stationary sleeve having at least one aperture. When the test assembly is in its open configuration the apertures of the sliding sleeve are aligned with the apertures of the stationary sleeve and fluid communication is provided through the aligned apertures. The sand screen assembly may also comprise a packer element.
The tubular member placed within the wellbore defines an annulus area. When the isolation assembly is in its closed configuration and the test assembly is in its open configuration, hydraulic communication between the annulus area above the packer and the interior of the isolation assembly can be achieved while also providing hydraulic isolation from the annulus area below the packer. The isolation assembly can comprise an isolation pipe and at least one seal element. When the isolation assembly is in its closed configuration, the isolation pipe forms a seal within the sand screen assembly and fluid communication through the sand screen assembly is restricted. The isolation assembly may comprise a shifting collet assembly attached to the tubular member that is capable of engaging with the isolation pipe. The shifting collet may include flex beam portions that are capable of engaging with the isolation pipe. The isolation assembly can also have a latching collet assembly that engages with the sand screen assembly when the isolation assembly is in its closed configuration.
The test assembly can comprise a test port and at least one seal assembly, where the test port and the seal assemblies are capable of aligning with the packer and the sand screen assembly to provide hydraulic communication of the interior of the isolation assembly with the annulus above the packer and hydraulic isolation from the annulus below the packer.
Another embodiment of the invention is a tool for isolating and testing a sand screen assembly within a wellbore comprising a tubing string disposed within the wellbore and forming a tubing-wellbore annulus, an isolation pipe assembly movable within the sand screen assembly and capable of being selectively positioned in an upper position and a lower position, and an isolation test tool attached to the tubing string and capable of being selectively positioned in an open configuration and a closed configuration. When the isolation pipe assembly is in its lower position, fluid communication through the sand screen assembly is restricted and when the isolation test tool is in its open configuration, hydraulic isolation between the isolation pipe assembly and the tubing-wellbore annulus is achieved.
The sand screen assembly may further comprise a packer element, and the isolation test tool may comprise a sliding sleeve having at least one test port. The isolation pipe assembly may be retained in its upper position by a releasable retaining element. The isolation pipe assembly can be shifted from its upper position to its lower position by means of a shifting collet connection with the tubing string. The isolation test tool may be held in its closed configuration by a retaining element.
Yet another embodiment of the invention is a method for isolating and testing a sand screen assembly in a wellbore from passage of fluids through it. The method comprises positioning an isolation pipe assembly within the sand screen assembly, positioning an isolation test tool attached to a tubing string within the wellbore, and shifting the isolation pipe assembly into a sealed position where the isolation pipe assembly is in sealing contact with the sand screen assembly, thereby restricting fluid flow through the sand screen assembly. The method further comprises shifting the isolation test tool to a testing configuration, and testing the integrity of the seal between the isolation pipe assembly and the sand screen assembly.
The isolation pipe assembly may comprise a sliding sleeve mechanism that is in sliding contact with the sand screen assembly. The shifting of the isolation pipe assembly can also utilize a shifting collet connected to the tubular string, and can include the imposition of a downward force on the tubular string that is transferred through the shifting collet connection onto the isolation pipe assembly. Once the isolation pipe assembly is shifted into its sealed position, the isolation pipe assembly can be retained in its sealed position by means of a retaining collet. The shifting of the isolation test tool may likewise include a further downward force on the tubular string that is transferred onto the isolation pipe assembly. The isolation pipe assembly and the isolation test tool may be held in their initial position by retaining elements, such as shear elements. The shifting of the isolation test tool to a testing configuration comprises aligning testing ports to an open position to create hydraulic communication between the isolation pipe assembly and an annulus region in the wellbore and can also comprise aligning at least one seal that isolates a cross-over port located within the sand screen assembly from hydraulic communication with the interior of the isolation pipe assembly. The testing of the integrity of the seal between the isolation pipe assembly and the sand screen assembly can include pressure testing of an annulus region in the wellbore that is in hydraulic communication with the interior of the isolation pipe assembly.
Still another embodiment is an isolated production pipe assembly formed according to a method comprising providing a non-isolated production pipe assembly in a wellbore, the non-isolated production pipe having a sand control screen, attaching a shifting collet housing assembly to an isolation pipe string assembly, and inserting the shifting collet housing assembly and isolation pipe string assembly into the non-isolated production pipe assembly. The method further comprises attaching a testing tool capable of being in a first configuration and a second configuration, a shifting collet assembly and a tubular string to form a work string. The work string is then inserting into the wellbore, thereby defining a work string-wellbore annulus, so that the shifting collet assembly engages the interior of the shifting collet housing assembly. A downward force is imparted on the work string to move the isolation pipe string assembly into a position where the isolation pipe string assembly is in sealing contact with the non-isolated production pipe assembly both above and below the sand control production screen. This converts the non-isolated production pipe assembly into an isolated production pipe assembly, wherein the isolated production pipe assembly in the wellbore prevents fluid flow through the sand control screen. A further downward force is applied on the work string to shift the testing tool from its first position to its second position, so that the testing tool provides hydraulic communication between the interior of the isolated production pipe assembly and the work string-wellbore annulus above the testing tool. The work string-wellbore annulus is then pressure tested to test the integrity of the isolated production pipe assembly.
The isolation pipe string assembly is retained in sealing contact with the non-isolated production pipe by means of a retaining collet device. The testing tool is capable of being held in its first position by means of a retaining element, such as a shear element that will break when a predetermined force is applied against it.
In yet another embodiment a method of gravel packing, isolating and testing a sand screen completion of a wellbore in a single trip is disclosed. This method comprises inserting into the wellbore a sand screen assembly, an isolation pipe, and a test assembly on a workstring, performing a gravel pack operation, and shifting the isolation pipe to a position in sealing contact with the sand screen assembly, thereby isolating the sand screen assembly. The test assembly is then shifted to a configuration that provides hydraulic communication between the interior of the isolation pipe and the workstring-wellbore annulus above the test assembly. The integrity of the seal between the isolation pipe and the sand screen assembly is then hydraulically tested by imposing pressure on the workstring-wellbore annulus at the surface.
The sand screen assembly can include a packer located above the sand screen. During the gravel pack operation carrier fluid returns are able to circulate to the surface through the sand screen, isolation pipe, test assembly, and workstring. The test assembly can comprise a test port and at least one seal assembly. When the workstring is used to shift the test assembly, the test port and the seal assemblies align with the packer and the sand screen assembly to provide hydraulic communication between the isolation pipe and the workstring-wellbore annulus above the packer while providing hydraulic isolation from the sand screen-wellbore annulus below the packer.
A particular embodiment involves a method of completing a well comprising isolating a sand screen assembly with isolation tubing, and testing the hydraulic seal of the isolated sand screen assembly through a test assembly.
The method may further comprise inserting a sand screen assembly, isolation tubing and a test assembly into the well on a workstring, shifting the isolation tubing into a sealed position within the sand screen assembly, shifting the test assembly into an open position, and pressure testing the workstring-well annulus to test the hydraulic seal of the isolation tubing within the sand screen assembly. A gravel pack operation may be performed and the well flow tested prior to isolating the sand screen assembly.